chore(deps): update external/libexpat digest to efa6739 #178

Job	Run time
lib_android (monero)	27m 1s
lib_android (wownero)	26m 0s
lib_darwin (monero)	13m 46s
lib_darwin (wownero)	13m 38s
ios build (monero)	15m 43s
ios build (wownero)	11m 38s
lib_linux (monero)	28m 21s
lib_linux (wownero)	28m 53s
macos build (monero)	3m 16s
macos build (wownero)	3m 19s
lib_mingw (monero)	3m 37s
lib_mingw (wownero)	3m 31s
lib_sailfishos_aarch64 (monero)	3m 8s
lib_sailfishos_i486 (monero)	2m 1s
lib_sailfishos_aarch64 (wownero)	3m 11s
lib_sailfishos_i486 (wownero)	2m 2s
create single release file	1m 0s
test ts library	48s
comment on pr	6s
	3h 10m 59s

Provide feedback